Belgian Pat. No. 832702 describes a class of 3-phenyl-5-substituted-4(1H)-pyridones which are broad spectrum herbicides. Included within the scope of the Belgian disclosure are many of the compounds prepared by the presently claimed process. The Belgian patent describes a process for the preparation of the pyridones which involves the same final step as the present process, i.e., the formation of the pyridone ring by formylation of an .alpha.-substituted acetyl-.beta.-aminostyrene followed by reaction with a primary amine. However, the present process differs markedly from that of the Belgian patent in the steps leading to the intermediate .alpha.-substituted acetyl-.beta.-aminostyrene.
Another of the steps of the present process, the reaction of bromoacetyl bromide with a .beta.-aminostyrene, is disclosed by Garcia et al., J. Heterocyclic Chem., 11, 219 (1974). Garcia's objective was the preparation of substituted indoles by way of o-nitrobenzylketones. There is no suggestion by Garcia et al., of the preparation of pyridones as described herein.